Patterns of male production in the favosa (, Meliponini) Tong Chinhinst, Gijs Grob, Francis Meeuwsen, Marinus Sommeijer

To cite this version:

Tong Chinhinst, Gijs Grob, Francis Meeuwsen, Marinus Sommeijer. Patterns of male production in the stingless bee Melipona favosa (Apidae, Meliponini). Apidologie, Springer Verlag, 2003, 34 (2), pp.161-170. ￿10.1051/apido:2003008￿. ￿hal-00891768￿

HAL Id: hal-00891768 https://hal.archives-ouvertes.fr/hal-00891768 Submitted on 1 Jan 2003

HAL is a multi-disciplinary open access L’archive ouverte pluridisciplinaire HAL, est archive for the deposit and dissemination of sci- destinée au dépôt et à la diffusion de documents entific research documents, whether they are pub- scientifiques de niveau recherche, publiés ou non, lished or not. The documents may come from émanant des établissements d’enseignement et de teaching and research institutions in France or recherche français ou étrangers, des laboratoires abroad, or from public or private research centers. publics ou privés. Apidologie 34 (2003) 161–170 © INRA/DIB-AGIB/ EDP Sciences, 2003 161 DOI: 10.1051/apido:2003008 Original article

Patterns of male production in the stingless bee Melipona favosa (Apidae, Meliponini)

Tong X. CHINHa,b*, Gijs B.J. GROBc, Francis J.A.J. MEEUWSENa, Marinus J. SOMMEIJERa

a Department of Social , Utrecht University, PO Box 80.086, 3508 TB Utrecht, The Netherlands b National Bee Research and Development Centre, Langha, Dongda, Hanoi, Vietnam c Nationaal Herbarium Nederland, Leiden University, PO Box 9514, 2300 RA Leiden, The Netherlands

(Received 4 April 2002; revised 3 August 2002; accepted 17 September 2002)

Abstract – In many stingless bee , laying workers oviposit trophic eggs that serve as a component of the queen’s diet. Workers of some species also lay reproductive worker eggs that give rise to males. Male- producing workers can occur in queenright colonies. We studied male production by workers of Melipona favosa. In six colonies monitored under field conditions, we observed that males emerged during distinct “Male Emerging Periods”. Subsequently, we studied the laying of male eggs in laboratory observation hives with the use of video. We found that laying workers oviposited reproductive eggs in distinct “Reproductive Laying Worker Periods” and that this was followed by the clumped mergence of males afterwards. Behaviours of laying workers and of the ovipositing queen are preliminarily described.

Melipona / laying worker / male production / reproductive eggs / trophic eggs

1. INTRODUCTION sons than to other worker’s sons (Ratnieks, 1988, Peters et al., 1999). The haplo-diploid system in social In colonies of the , Apis mellifera, influences the relatedness of which are headed by a highly polyandrous queens and workers to males and can queen, males are normally produced only by contribute to conflict over male production. In the queen (Seeley, 1985; Peters et al., 1999). the light of the kin selection theory (Hamilton, In queenless colonies, honeybee workers can 1972), when a colony is headed by a single activate their ovaries and lay unfertilised eggs. monandrous queen, workers are expected to Workers in queenright colonies generally do favour their sons (relatedness, r = 0.5) or other not activate their ovaries as a result of worker’s sons (nephews) (r = 0.375) above pheromonal control by the queen (Velthuis, sons of the queen (brothers) (r = 0.25) 1970). However, it has recently been (Hamilton, 1964; Ratnieks, 1988, Peters et al., demonstrated that queen-right Apis mellifera 1999). In contrast, in colonies headed by workers sometimes do lay eggs but that their polyandrous queens, worker-queen conflict contribution to male production is low because over male production may be reduced because of worker policing (Barron et al., 2001; workers are then more related to the queen’s Ratnieks,1993; Visscher, 1989).

* Correspondence and reprints E-mail: [email protected] 162 T.X. Chinh et al.

In contrast to Apis, stingless bee both the queen and the workers, and try to (Meliponini) workers with active ovaries are explain the observed patterns in light of exist- common in queenright colonies (Sakagami, ing theories. 1982). Moreover, worker oviposition in queenright colonies occurs widely among the various groups of stingless bees (Sakagami, 2. MATERIALS AND METHODS 1982; Sommeijer and van Buren, 1992; Imperatriz-Fonseca and Kleinert, 1998; All colonies of M. favosa were kept in wooden Koedam et al., 1999). However, in queenright box hives (W × L × H: 20.5 × 35.5 × 15 cm), which colonies, Melipona workers may lay mostly were covered by glass lids facilitating behavioural trophic, not reproductive eggs (Sakagami, observation. The mature brood combs were 1982; Sommeijer et al., 1984a). Trophic eggs partially separated from the major brood-nest by are eaten by the queen prior to her oviposition, placing them in small annex boxes that were while reproductive eggs can give rise to off- connected to the major nest box with plastic tubes. spring. The annex served as a place where newly emerged bees could remain for about the first 24 hours after In some species of non-Melipona stingless their emergence on the comb. Recently eclosed bees, e.g., in Scaptotrigona, reproductive workers and males of M. favosa do not disperse workers commonly oviposit after queen ovi- from the comb of emergence. Upon the recording of position (Beig, 1972; Bego, 1982; Sakagami, daily-emerged adults, these were reintroduced into 1982), which leads to cells containing both a the main brood-nest compartment. Colony worker egg and a queen egg. In contrast, in development parameters such as daily cell Melipona, oviposition by reproductive laying production, numbers of new cells and storage pots, workers generally precludes oviposition by the etc., were measured weekly. queen in the same cell (Sommeijer et al., The field studies were carried out from October 1984b; Sommeijer and van Buren, 1992). 1994 to February 1995 on the island of Tobago Reproductive workers of M. favosa may also (Trinidad and Tobago, West Indies). Six queenright colonies of Melipona favosa that earlier had been oviposit after queen oviposition, however this installed in a room in a wooden building were used phenomenon is very rare. to study the temporal patterns of male production. Melipona trophic and reproductive worker These colonies had free flight to the outside in their eggs differ in their external morphology. natural habitat through plastic tubes leading Reproductive eggs in queenright colonies through the wall. The colonies received no resemble reproductive worker eggs layed additional feeding. The colonies had been in this in queenless colonies (van Buren and position for more than two years. The population of these colonies ranged from 129 to 204 bees, which Sommeijer, 1988), and have a well-developed is normal for this species. chorion. In contrast, the chorion of trophic eggs is poorly developed. However, these In 1997, four queenright colonies (referred to as 7, 8, 9 and 10) of M. favosa were housed in the room differences are graded and not discrete of our laboratory at the Faculty of Biology, Utrecht (Sommeijer et al., 1984a). Besides a difference University, The Netherlands. These colonies in trophic and reproductive egg morphology, originated from Trinidad and Tobago and their there is a difference in the behaviour of populations ranged from 109 to 270 bees1 workers that lay trophic and reproductive Temperature was kept constantly at 24 degrees eggs, so the two categories of laying workers Celsius and RH was constantly around 75%. In can be easily distinguished (Sommeijer and these lab colonies, all ovipositions were analysed to van Buren, 1992). identify whether the queen or a worker oviposited in a cell. Red light and video were used to observe We have studied the production of males in the ovipositions, comb development and adult M. favosa. In a previous paper we showed that emergence continuously and simultaneously from in M. favosa the workers are the main produc- April to November. To identify the maternity of the ers of males (Sommeijer et al., 1999). In this emerged bees, the location of each oviposited cell paper we describe the production of males in more detail and show that it occurs periodi- 1 The colonies studied in the Utrecht lab had an cally both under field and laboratory condi- average population of 194 and were larger than the tions. In the discussion we link this clumped colonies studied in the field (average population 161), male production to oviposition behaviour of but this difference was not significant (P > 0.05). Observations on male production in Melipona favosa 163

Table I. Some parameters of all the fifteen observed Male Emerging Periods in the field and in the lab. MEP Colony Start End Duration Males % Males Intervals Abs. max Rel. max (day) (day) 1 1 11 Nov 3 Jan 53 153 14.6 9 1 Dec 10 Dec 2 1 24 Jan 23 Feb 30 92 13.4 2 4 Feb 8 Feb 3 2 24 Nov 8 Dec 14 8 11.0 1 1 Feb 1 Dec 4 2 17 Jan 23 Feb 37 62 15.3 1 27 Jan 26 Jan 5 3 19 Dec 15 Feb 74 88 18.1 6 17 Jan 17 Jan 6 4 15 Nov 19 Dec 35 19 9.7 5 26 Dec 18 Dec 7 4 24 Jan 23 Feb 30 79 16.0 2 14 Feb 1 Feb 8 5 31 Oct 17 Nov 17 43 23.2 1 11 Dec 14 Nov 9 5 29 Dec 22 Jan 24 12 3.6 4 13 Jan 4 Jan 10 5 11 Feb 21 Feb 10 14 14.9 1 17 Feb 11 Feb 11 6 16 Dec 22 Jan 37 69 37.3 2 3 Jan 2 Jan 12 7* 12 May 27 Jun 46 422 70.7 0 25 May 17, 19, 24 May 13 8* 8 Sep 17 Oct 38 163 38.0 1 21 Sep 29, 23 Sep 14 9* 10 Apr 16 Jun 67 940 10.0 3 21 Apr 23, 24 Apr; 3 Jun 15 10* 9 Sep 7 Dec 60 192 33.8 5 10 Oct 10, 16, 17 Oct Average 38.1 157.1 22.0 2.9 St.dev. 19.0 240.9 17.0 2.5 * Colonies in the lab. MEP: index number given to the Male Emerging Period. Start: the date on which the MEP starts, End: the date on which the MEP ends, Duration: The duration of the MEP in days, Males: the total number of males emer- ging during the MEP, % Males: the number of males emerging during the MEP as a percentage of the total number of emerging bees during the MEP. Intervals: the number of periods of no male production within MEPs of 1 day or more. Abs.max.: the date on which the absolute number of emerging males reaches its peak, Rel.max.: the day on which the % of emerging males reaches its peak. was mapped and its development followed until and worker oophagy as they try to operculate emergence. after their own oviposition. 5. Worker oviposition after queen oviposition, followed by immediate operculation by this Classification of oviposition types laying worker. The following classification of provisioning and oviposition processes (POPs) was made during this study: 3. RESULTS 1. Exclusive queen oviposition. 2. Worker oviposition followed by queen oviposition. In this case the worker laid a trophic 3.1. Male emerging periods worker egg (TWE), which was followed by in the colonies under field condition subsequent laying worker withdrawal, queen oophagy, and queen oviposition. The analysis of emerging bees of the 3. Reproductive worker oviposition. This is different sexes and castes in the field revealed oviposition by a laying worker that does not that males emerged regularly in repeated withdraw after oviposition but operculates the periods that we define as “Male Emerging cell immediately. This excludes queen oophagy and queen oviposition, and there is no obvious Periods” (MEPs) (Fig. 2). In the six field- response of the queen to this. observed colonies, 11 MEPs were recorded, 4. Oviposition competition. In this case various which occurred nonsynchronously in different laying workers are competing for oviposition colonies (Tab. I). A typical MEP (Fig. 1) is 164 T.X. Chinh et al.

100 males 80 Figure 1. The typical 60 pattern of an occur- ring MEP is presen- emerging 40 ted for colony 10 as of

20 an example. The emerging males are 0 given by percentages 31-Jul 10-Aug 20-Aug 30-Aug 9-Sep 19-Sep 29-Sep 9-Oct 19-Oct 29-Oct 8-Nov of daily emerging Percentage Dates bees. characterised by a gradual increase of the daily ranged from 3.6% to 37.3%, with an average number of emerging males. After reaching of 16.1% (SD = 8.6, n = 11). The average peak values (sometimes with 100% males percentage of emerging males over all MEPs emerging daily) the percentage of daily was 15.6% (SD = 19.2, n = 265). The total emerging males declines to zero. However, number of males emerging during one MEP some MEPs were interrupted with short ranged from 8 to 153, with an average of 58.1 intervals from 1 to 9 days in which no males (SD = 44.7, n = 11). The values for the emerged. The occurrence of the MEPs differed individual colonies are presented in Table I. in the colonies. The length of the MEPs varied The periods between the recorded MEPs in from 10 to 74 days with an average of which exclusively females emerged ranged 32.8 days (SD = 18.3, n = 11) (Tab. I, Fig. 2). from 20 to 40 days with an average of Absolute and relative numbers of males 31.8 days (SD = 10.6, n = 5). emerging in a single MEP varied from day to day. The number of emerging males found on 3.2. Distinct reproductive laying worker one day ranged from 1 to 12 with an average periods of 2.1 (SD = 2.6, n = 265) over all MEPs. The number of emerging males as a percentage of The comprehensive observation of oviposi- the total number of emerging bees per MEP tions in the colonies at the Utrecht laboratory

Figure 2. Male emerging periods as they occurred in the different colonies observed in the field (black bars: MEPs). Observations on male production in Melipona favosa 165

Figure 3. Reproductive laying worker periods and male emerging periods occurred in the different colonies observed in the lab (thin bars: RLWPs, thick bars: MEPs). revealed that laying workers oviposited a duration of 46, 47, 102 and 59 days reproductive worker eggs (RWEs) in clearly respectively. distinct periods. We define such a period, which has a duration of about several weeks, 3.3. Oviposition rates fluctuate as a “Reproductive Laying Worker Period” with RLWPs (RLWP). These RLWPs occurred in all observed lab colonies; during the observation The average number of new cells per day time, a total number of four RLWPs occurred was significantly higher in the RLWP in the four colonies (Fig. 3). By definition, (average = 14.7, SD = 6.9, n = 185, range: outside the RLWPs the workers layed no 0–40) than in the periods where only queen reproductive eggs at all; only trophic eggs eggs were operculated (average = 10.1, SD = were layed. In one complete period of 44 days 6.0, n = 67, range: 1–32) (Anova, P < 0.0001). outside the RLWP that we could observe in Furthermore, the average egg production by colony 8 the queen did not produce any males. the queen in the RLWP (average = 7.9, In the other colonies we could not analyse the SD = 5.5, n = 185 days, range: 0–28) was also complete periods outside the RLWPs, but significantly less (Anova, P < 0.01) than from the observed parts of these periods it outside the RLWPs. In both these periods, appears that from the queen eggs operculated trophic worker eggs (TWEs) were laid and the in these periods exclusively female bees queen always ate such eggs. However, the emerged. daily percentage of TWEs per new cell in the RLWPs (average = 16.1, SD = 20.9%, n = 185, Unfortunately, because of the limitation of range: 0–80%) was significantly lower than our detailed observation time, we could not outside the RLWPs (average = 19.1, measure the whole length of all these non- SD = 28.3%, range: 0–200%) (Anova, RLWPs. P < 0.05). The daily number of TWEs In the RLWPs the daily number of RWEs (average = 1.6, SD = 2.5, range: 0–10, n = 185) varied and ranged from 0 to 35, with an positively correlated with the number of queen average of 6.8 (SD = 6.7, n = 185 days). The eggs (average = 7.9, SD = 5.5, range: 0–28), daily number of oviposited cells by both the (Spearman-r = 0.68, P < 0.0001, n = 185 days,) mated queen and the laying workers during whereas the daily number of RWEs was RLWPs ranged from 2 to 40, with an average obviously negatively correlated with the daily of 14.7 (SD = 6.9, n = 185 days). The RLWPs TWE number (Spearman-r = – 0.21, P < 0.01, of Col. 7, Col. 8, Col. 9 and Col. 10 had n = 185 days) in the RLWPs. 166 T.X. Chinh et al.

3.4. Number of observations of the five number of emerging males varied from day to classes of POPs day. The absolute number of emerging males per day ranged from 0 to 45, with an average Laying workers and the mated queen had a of 8.1 (SD = 9.3, n = 213) over all MEPs. In the different oviposition time for releasing their MEPs of colonies Col. 7 and Col. 9, most of various types of eggs. Laying workers took the emerging bees were males. On some days longer for the release of RWEs (average = only males emerged. In contrast, in the MEPs 8.9 s, SD = 2.6, n = 571, range: 4–31 s) than of Col. 8 and Col. 10 most of the emerging for ovipositing TWEs (average = 4.2s, SD = bees were females. The total number of males 1.4, n = 295, range: 4–31 s), (P < 0.001). produced during a single MEP ranged from Correlating the duration of the oviposition of 163 to 940 males, with an average of 429.3 the queen with the sex of her offspring it (st.dev.= 359.7, n = 4). The total number of appeared that her oviposition act took a shorter males emerging in the four recorded MEPs amount of time for the release of a fertilised was 1712. The relative number of emerging egg (average = 26.9 s, SD = 6.9, n = 1174, males as a percentage of the total number of range: 12–69 s) than for that of an unfertilised emerging bees per MEP ranged from 33.8 to egg (average = 46.1 s, SD = 35.8, n = 33, 70.7%, with an average of 53.1% (SD = 20.0, range: 21–181), (P < 0.01). n = 4). The length of the MEP ranged from 38 In general, the number of observed to 67 days (average = 52.8, SD = 13.0, n = 4). instances of the five oviposition classes were: In Col. 8, two MEPs were observed but the 1. Exclusive queen oviposition (n = 1698). first MEP was in process upon the arrival of 2. Worker oviposition followed by queen this colony at our lab, so its actual length was oviposition (n = 446). unknown (MEP recorded from May 12 to July 4). The values for the individual colonies 3. Reproductive worker oviposition (n = are presented in Table I. 1248). 4. Oviposition competition (n = 26). 5. Worker oviposition after queen oviposition 4. DISCUSSION (n = 2). This was only observed twice and only in the RLWP of Col. 9 in which the old queen died. In this colony, at the end of the recorded Our results indicate that in M. favosa males RLWP, a number of workers competed to are produced in distinct periods, the Reproduc- various degrees for oviposition, for feeding on tive Laying Worker Periods (or RLWPs), eggs of other workers, and for operculation in which lead to the clumped emergence of males some cells Shortly after this, the old queen of in distinct Male Emerging Periods (or MEPs). this colony died and a new queen became This periodic pattern of male production accepted, developed physogastry and took occurs both in the field and in the laboratory, over the ovipositions. This queen had and thus occurs even in the absence of extrani- exclusively male offspring, since she was dal cues, like fluctuations in temperature, unmated. In this colony, the old and the young sunlight, food availability and the like. Lab queen were observed together in the brood conditions consisted of constant photoperiods nest for almost two weeks. for day and night and did not mimic field conditions. 3.5. Reproductive laying worker periods Another important observation is that under (RLWPs) observed to be followed both laboratory and field conditions different by male emergence periods (MEPs) colonies appear not to be synchronous in their male production. When certain colonies are In the colonies at our Utrecht laboratory we producing males, others that are under the could confirm that RWEs were released in same condition are not, even when they are distinct RLWPs and that these were followed located in the vicinity of each other. Colonies by the emergence of males during typical appear to have their own rhythm for male MEPs after the incubation time (see Fig. 3). In production periods and a single colony may these MEPs, both the absolute and the relative have a number of MEPs over the year. Observations on male production in Melipona favosa 167

In addition, our results show that the brood rainy season due to floral scarcity in this cell production in the RLWP is higher than period. that outside these periods. This is because in We have no information about the age of the RLWP both the queen and laying workers the queens in the colonies studied in the natu- lay reproductive eggs. Since bees were not ral condition and in the colonies transported to individually marked, we could not determine The Netherlands. The age of queens was also the individual participation in cell construc- unknown in other, long established, colonies tion, provisioning and worker oviposition. where similar periodicity of male production But, besides this increase in brood production, by workers was observed in 1998 (Sommeijer we were not able to find any correlation and de Bruijn, personal observation). This between the occurrence of RLWPs and suggests that this periodicity may occur over other intranidal factors such as the number of the life of the queen. storage pots or production of queens. Finally, we observed that in M. favosa 4.2. The ‘switch-point’ hypothesis workers are the main producers of males (Sommeijer et al., 1999) and that, in In the bumble-bee, Bombus terrestris L., agreement with Kerr, 1969, the queen-worker queen-worker conflict over male parentage conflict is not expressed in overt aggression, usually follows a ‘switch point’, which occurs with exception of queenless and nearly when the queen starts laying haploid eggs queenless colonies. What causes the ‘internal (Duchateau and Velthuis, 1988; Bourke and rhythm’ of colonies in their male production? Ratnieks, 2001). This could explain the In the discussion below we will propose and observed patterns in M. favosa: the queen lays evaluate a few hypotheses, in the light of a haploid egg and becomes a competitor with circumstantial evidence and the worker-queen the workers, who start laying reproductive conflict over male parentage. eggs (the beginning of a RLWP). The RLWP may stop when the mass male production is at 4.1. Male production in M. favosa the expense of worker production. Worker is not seasonal production declines during a RLWP since the queen lays fewer diploid eggs. In Tobago we recorded MEPs occurring from the beginning of the observation period 4.3. Incomplete queen control in October to the end of the observation period hypothesis in February. The recorded MEPs in colonies studied in the Netherlands were from March Foster et al. (2001) discuss how queen (immediately from the arrival of the colonies) control in Dolichovespula colonies, headed by through the end of October. From these a monandrous queen, could result in fewer results and from unpublished observations males being produced by workers than by the in long established colonies in the natural queen. However, the pheromonal queen habitat (Sommeijer and de Bruijn, personal control could be evolutionarily unstable, if observation), it appears that in M. favosa workers were selected to ignore the pherom- males are produced in batches throughout the one (Keller and Nonacs, 1993; Foster et al., year. M. favosa is not unique for not having a 2001). Sommeijer et al. (1984) hypothesized strict seasonal male production. M. beecheii queen control in M. favosa. Diminishing (van Veen et al., 1999), queen control in colonies that are seasonally (van Benthem et al., 1995) and some becoming larger would lead to the develop- species (Beig, 1972; Bego, 1982, 1990; Engels ment of reproductive workers. However, in and Engels, 1984) are reported to produce this study, reproductive workers were clearly males throughout the year as well, yet in observed in all colonies. Moreover, RWE different numbers, depending on the season. laying did not occur in absence of the queen. Van Veen et al. (1999) found a significant Neither was there overt aggression between correlation between drone production and reproductive workers and the queen. The pollen storage in M. beecheii and male queen was present at most occurrences of production decreased at the end of the RWE laying but she was far less involved in 168 T.X. Chinh et al. such POPs than during her own egg-laying or workers may be able to develop such queen- the laying of TWEs. From the observations it like reproductive behaviour. appears that in the RLWPs the queen is much In contrast to many Hymenoptera, workers less motivated to play an active role in POPs are the main producers of males in M. favosa. than as she is outside these periods. The tem- Apparently queen control of male production porary occurrence of RLWs could result from is less pronounced in this species, or worker incomplete “queen control” over reproductive reproduction is much less costly for colony development in workers. Perhaps the tempo- reproduction in M. favosa than in other rary “worker-dominance” in M. favosa is the Hymenoptera. The general occurrence of arbitrary outcome of an arms race in favour of reproductive workers is consistent with the the workers (Foster et al., 2001). In this case it hypothesis that M. favosa colonies are headed may very well be that closely related species by monandrous queens. It remains to be tested do not show the same patterns (Foster et al., how general this phenomenon is in Melipona 2001). Indeed, M. beecheii seems to have a and other stingless bees. It is important to more seasonal male production (Moo-Valle study the proximate and ultimate function of et al., 2001; van Veen, 1999). In any case, it this periodical male production by workers in remains unclear why and how queen control these stingless bees. would diminish frequently and during rela- tively short periods.

ACKNOWLEDGMENTS 4.4. Queen-like worker hypothesis The observations in Tobago (G.B.J. Grob, 1994- It has been established (Sommeijer and 1995) were carried out with the co-operation of the Tobago House of Assembly and Mr. Gladstone Velthuis, 1977) that in queenless colonies of Solomon, Tobago Apicultural Society. The subse- M. favosa, some workers behave in a queen- quent Utrecht laboratory studies (October 1996 to like manner: they can start a POP and are March 1998) which comprised the MSc study of the responsible for many ovipositions. Through first author, were supported by a fellowship from the genetic-trophic caste determination system NUFFIC (Netherlands Universities Foundation for in Melipona (Velthuis and Sommeijer, 1991) it International Cooperation). may be that, also in queenright colonies, some workers are genetically more fit to become Résumé – Production périodique de mâles chez reproductive than others. According to this l’abeille sans aiguillon Melipona favosa (Apidae, hypothesis, only the limited number of Meliponini). Chez de nombreuses espèces workers with a genetic predisposition to d’abeilles sans aiguillon les ouvrières pondeuses develop into queens, could be responsible for pondent des œufs trophiques qui sont utilisés comme élément du régime alimentaire des reines. all RWEs. Probably the individual oviposition Les ouvrières de certaines espèces pondent aussi performance of these reproductive workers des œufs d’ouvrières reproducteurs qui donnent can exceed the oviposition rate of workers naissance à des mâles. Les ouvrières qui produisent that release TWEs (Sommeijer and van des mâles se rencontrent même dans des colonies Buren, 1992). Most likely, the number of avec reine. Après avoir trouvé que les ouvrières reproductive laying workers is limited per pondeuses sont les principales productrices de colony. It may be assumed that these queen- mâles dans les colonies de Melipona favosa, nous cherchons à connaître la façon dont sont produits les like workers are able to escape from queen mâles dans le temps. Pour cela nous avons mené des pheromonal control. These workers cannot observations comportementales sur des colonies sur start a POP in queenright situations, but they le terrain pour enregistrer l’émergence des mâles can take one over. Pheromonal control may des rayons de couvain. Par la suite, nous avons occur in these queen-like workers and prevent étudié en grand détail la ponte dans un grand overt aggression by the queen and perhaps also nombre de cellules individuelles dans des colonies maintenues dans notre laboratoire aux Pays-Bas by their fellow-workers. According to this pour analyser la maternité des mâles susceptibles hypothesis, the end of a RLWP is results from d’émerger de ces cellules. Pour cela nous avons the cessation of activity by these specific utilisé des enregistrements vidéo et un éclairage en laying workers and after some time, some new lumière rouge. Dans une série de six colonies en Observations on male production in Melipona favosa 169 conditions naturelles nous avons trouvé que Erklärung dieses typischen Ablaufs der Erzeugung l’émergence des mâles avait lieu à différentes von Männchen durch Arbeiterinnen werden « périodes d’émergence des mâles » (PEM) diskutiert. (Figs. 1 et 2). En étudiant la ponte des œufs de mâles dans des ruches d’observation au laboratoire Melipona / legende Arbeiterinnen / Erzeugung à l’aide de la vidéo, nous avons trouvé que les der Männchen / reproduktive Eier / trophische ouvrières pondeuses pondaient leurs œufs au cours Eier de différentes « périodes d’ouvrières pondeuses reproductrices » et que ces périodes étaient suivies par l’émergence en bloc des mâles REFERENCES (Fig. 3). Le tableau I donne les caractéristiques des PEM. 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Insectes Soc. 4, 285–290. werden, untersuchten wir, ob ein zeitliches Muster Duchateau M.J., Velthuis H.H.W. (1988) Devel- bei der Erzeugung von Männchen besteht. Dazu opment and reproductives strategies in Bombus führten wir zunächst Verhaltensbeobachtungen bei terrestris colonies, Behaviour 107, 186–207. Völkern im Freiland durch und protokollierten das Schlüpfen der Männchen aus den Brutwaben. Engels E., Engels W. (1984) Drone congregation near the nest of the stingless bee Scaptotrigona Anschließend untersuchten wir genau die Eiablage postica, Apidologie 15, 315–328. bei einer großen Anzahl einzelner Zellen in Völkern, die in den Niederlanden im Labor Foster K.R., Ratnieks F.L., Gyllenstrand N., Thoren gehalten wurden, um die Mütter der aus diesen P.A. (2001) Colony kin structure and male production in Dolichovespula wasps, Mol. Ecol. Zellen schlüpfenden Männchen zu bestimmen. Die 10, 1003–1010. Beobachtungen wurden mit Video und bei roter Beleuchtung durchgeführt. Bei sechs Völkern im Hamilton W.D. (1964) The genetical evolution of Freiland stellten wir fest, dass die Männchen in social behaviour. I, J. Theor. Biol. 7, 1–16. distinkten Zeitabschnitten schlüpften, den Hamilton W.D. (1972) Altruism and related “Schlupfperioden der Männchen” (Abb. 1 und phenomena in social insects, Annu. Rev. Ecol. Abb. 2). Bei den späteren Beobachtungen mit Syst. 3, 192–232. der Video Kamera im Labor über das Legen Imperatriz-Fonseca V.L., Kleinert A.M.P. (1998) der Männcheneier fanden wir, dass legende Worker reproduction in the stingless bee species Arbeiterinnen reproduktive Eier während einer Friesella schrottkyi (Hymenoptera: Apidae: distinkten “Reproduktiven Periode der legenden Meliponinae), Entomol. Gen. 23, 169–175. Arbeiterinnen” erzeugten und dass später die Keller L., Nonacs P. (1993) The role of queen Männchen in Gruppen schlüpften (Abb. 3). Die pheromones in social insects: queen control or Merkmale der “Schlupfperioden der Männchen” queen signal?, Anim. Behav. 45, 787–794. (MEP) werden beschrieben (Tab. I). Im Freiland Kerr W.E. (1969) Some aspects of the evolution of gibt es keine Synchronisation innerhalb der Völker social bees (Apidae), Evol. Biol. 3, 119–175. in Bezug auf die MEPs, obwohl sie im selben Koedam D. (1999) Production of queens, workers and Gebiet nisten. Verschiedene Hypothesen für eine males in the stingless bee Melipona favosa 170 T.X. Chinh et al.

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